Celeris
Completely offline wallet ecosystem.
The problem Celeris solves
The Problem It Solves
UPI and mobile payment systems rely heavily on internet connectivity and bank servers. In rural areas or spots with weak networks—like remote zones or parts of campuses—UPI often fails. Server downtimes during peak hours make things worse. NFC-based payments try to solve this but aren't supported by many budget or older devices. Also, UPI has daily limits that slow down high-frequency users and small vendors.
Our Solution
We built an offline wallet and payment app that works without constant internet or NFC. Users load money into the app wallet when online. After that, peer-to-peer payments work entirely offline via encoded SMS messages. Android's BroadcastReceiver listens for these and processes transactions.
Each payment is confirmed via SMS and reflected in the app instantly. When the user is back online, transaction history syncs with our secure server.
What People Can Use It For
- Payments in poor-network areas
- Digital transactions without internet
- Devices without NFC
- Microtransactions without UPI limits
- Reliable backups synced when online
Why It’s Better
- Works offline, no real-time server needed
- No dependency on NFC or internet
- Inclusive for low-end devices
- Real-time confirmations via SMS
- Smooth sync and record keeping
Our solution brings consistent, secure digital payments to places and people where existing methods fail.
Challenges we ran into
We had to shift from React Native to Native Kotlin because Android had blocked cross-platform applications to use native dependencies. Another problem was the main part of the project, the SMS server. It was initially Twilio, but we cannot send messages to Twilio, so we had to set up our own SMS server to do all the tasks for the SMS.
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